Question: $ { \left[\begin{array}{r}{1} \\ {-2} \\ {-1}\end{array}\right]-\left[\begin{array}{r}{-1} \\ {-1} \\ {4}\end{array}\right] = {?} } $
Answer: To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{r}{1}-{-1} \\ {-2}-{-1} \\ {-1}-{4}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{r}{2} \\ {-1} \\ {-5}\end{array}\right]}$